net: phy: at803x: add support for cdt cross short test for qca808x

QCA808x PHY Family supports Cable Diagnostic Test also for Cross Pair
Short.

Add all the define to make enable and support these additional tests.

Cross Short test was previously disabled by default, this is now changed
and enabled by default. In this mode, the mask changed a bit and length
is shifted based on the fault condition.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>